nfsd: Fix memory leak in nfsd_getxattr

Fix a memory leak in nfsd_getxattr. nfsd_getxattr should free up memory
	that it allocated if vfs_getxattr fails.

Signed-off-by: Krishna Kumar <krkumar2@in.ibm.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>